Geometry calculator

Perimeter Calculator

Find the outside boundary length of common 2D shapes.

Use calculator View formulas FAQ

Calculator

Enter dimensions

Select a shape where available, choose units, and read the result as dimensions update.

Geometry

Shape
Width m
Height m
Side A m
Side B m
Side C m
Diameter m
Number of sides
Side length m

Result

About this calculator

How it works

Perimeter is the total distance around a 2D shape. It is useful for layout, fencing, weld length, trim, material takeoff, and geometry checks.

Formulas

Formulas used

Rectangle

P = 2 (w + h)

Triangle

P = a + b + c

Circle

P = pi d

Regular polygon

P = n s

Worked example

Example: 2.4 m by 1.2 m rectangle

For a rectangular panel with width 2.4 m and height 1.2 m:

Perimeter

P = 2 x (2.4 + 1.2) = 7.2 m

Area check

A = 2.4 x 1.2 = 2.88 m2

Guide

How to use this calculator

Select the shape or section type if a shape menu is shown.
Enter the known dimensions and choose units beside each length input.
Read the highlighted result first, then use the supporting values for related checks.

Reference

What the results mean

Perimeter

The total length around the outside boundary.

Area check

The enclosed surface area, useful as a supporting value for rectangles and circles.

Assumptions and limits

Before using the result

Inputs are treated as ideal geometric dimensions with no tolerance, chamfer, fillet, draft, roughness, or manufacturing allowance.
Section properties are centroidal for the listed standard shapes and do not include rotation, offsets, or parallel-axis corrections.
Use project drawings, tolerances, material data, and applicable design standards for final engineering work.

FAQ